| Cenozoic volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, China： Petrochemical evidence for partial melting of the mantle-crust transition zone |
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| 作者姓名： | LAI Shaocong QIN Jiangfeng LI Yongfeng LIU Xin |
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| 作者单位： | LAI Shaocong，QIN Jiangfeng，LI Yongfeng，and LIU Xin State Key Laboratory of Continental Dynamics，Department of Geology，Northwest University，Xi'an 710069，China |
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| 基金项目： | 国家自然科学基金
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Teaching and Research Award Program for Outstanding Young Teachers at Higher Education Institutions |
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| 摘 要： | Neogene volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, are represented by a typical intermediate-basic and intermediate alkaline rock association, with latite-trachyte as the main rock type. The results of chemical analysis are: SiO2=52%–62%, Al2O3>15%, Na2O/K2O>1 and MgO<3.30%. In addition, the volcanic rocks are LREE-enriched with LREE/HREE=10–13, (La/Yb)N=15–19, and show a weak negative Eu anomaly with δEu=0.71–0.89. The close relationship between Mg# and SiO2 and the co-variation of the magmatophile elements and ultra-magmatophile elements such as La/Sm-La and Cr-Tb indicate that this association of volcanic rocks is the product of comagmatic fractional crystallization. The rock association type and lower Sm/Yb values (Sm/Yb=3.23–3.97) imply that this association of volcanic rocks should have originated from partial melting of spinel lherzolite in the lithospheric mantle. On the other hand, the weak negative Eu anomaly and relative depletion in Nb, Ta and Ti reflect the features of terrigenous magma. So the Neogene Belog Co alkaline volcanic rocks should be the result of partial melting of the special crust-mantle transition zone on the Qinghai-Tibet Plateau.
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| 关 键 词： | 新生火山岩石 地幔 变迁地带 青藏高原 |
| 收稿时间： | 10 April 2006 |
| 修稿时间： | 2006-04-102006-06-20 |
Cenozoic volcanic rocks in the Belog Co area,Qiangtang, northern Tibet,China: Petrochemical evidence for partial melting of the mantle-crust transition zone |
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| LAI Shaocong QIN Jiangfeng LI Yongfeng LIU Xin.Cenozoic volcanic rocks in the Belog Co area,Qiangtang, northern Tibet,China: Petrochemical evidence for partial melting of the mantle-crust transition zone[J].Chinese Journal of Geochemistry,2007,26(3):305-311. |
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| Authors: | Lai Shaocong Qin Jiangfeng Li Yongfeng Liu Xin |
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| Institution: | (1) State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069, China |
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| Abstract: | Neogene volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, are represented by a typical intermediate-basic and
intermediate alkaline rock association, with latite-trachyte as the main rock type. The results of chemical analysis are:
SiO2=52%–62%, Al2O3>15%, Na2O/K2O>1 and MgO<3.30%. In addition, the volcanic rocks are LREE-enriched with LREE/HREE=10–13, (La/Yb)N=15–19, and show a weak negative Eu anomaly with δEu=0.71–0.89. The close relationship between Mg# and SiO2 and the co-variation of the magmatophile elements and ultra-magmatophile elements such as La/Sm-La and Cr-Tb indicate that
this association of volcanic rocks is the product of comagmatic fractional crystallization. The rock association type and
lower Sm/Yb values (Sm/Yb=3.23–3.97) imply that this association of volcanic rocks should have originated from partial melting
of spinel lherzolite in the lithospheric mantle. On the other hand, the weak negative Eu anomaly and relative depletion in
Nb, Ta and Ti reflect the features of terrigenous magma. So the Neogene Belog Co alkaline volcanic rocks should be the result
of partial melting of the special crust-mantle transition zone on the Qinghai-Tibet Plateau. |
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| Keywords: | major and trace elements Cenozoic volcanic rock mantle-crust transition zone Qinghai-Tibet Plateau |
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